A geomorfologia fluvial e a conectividade na planície de inundação da Ilha do Careiro (Careiro da Várzea – AM)

Abstract

The Careiro Island is located near at the confluence of the Negro and Solimões rivers, within the Amazon basin, and is characterized as a typical floodplain environment. Its hydrological regime is strongly influenced by the Solimões morphodynamic system, which represents the main source of water and sediments to the island. Hydrological seasonality plays a significant role in controlling the fluvial connectivity of the floodplain, thereby conditioning the dynamics of the inundated surface and the processes of sediment transport and deposition. Due to recent extreme hydroclimatic events, such as the 2021 flood and the drought of 2024, the watercovered surface underwent significant changes on the island. In this context, this research aimed to analyze the influence of fluvial processes on the morphodynamics of the Careiro Island between 2021 and 2024. To achieve this, water surface maps, precipitation, water discharge of the Solimões River, water-level of the Negro River, suspended sediment concentration (SSC) and building data from IBGE, were analyzed. High spatial resolution satellite images from the PlanetScope and Sentinel-2 MSI sensors were also used to map fluvial connectivity points and geomorphological units on the island. The results reveal significant changes in the fluvial landscape during the study period, including 43% reduction in the mapped water surface between the 2021 flood and the 2024 drought. It was found that the highest frequency of fluvial connectivity and suspended sediment input occurs in the downstream sector of the island, with the channel “Furo do Rei” standing out as the main connection between the Amazonas River and the island’s interior. This connection promotes the transport of suspended sediments from the Solimões River and their deposition within the island. The annual average SSC of the lakes on Careiro Island was estimated at 54 mg/L, about 35% lower than the annual average SSC of the Solimões River. The fluvial landscape is characterized by the presence of lakes, channels, and paranás, which enhance hydrological connectivity, as well as by the occurrence of paleochannels. Among the identified geomorphological units, lakes are predominant, followed by channels and sandy bars. It is concluded that the main changes in the fluvial landscape of Careiro Island are associated with water level variability of Amazon River, a hotspot of connectivity points in the downstream sector, and the occurrence of mass movement (“terras caídas”) along the margins directly influenced by the Solimões river.